This invention relates to industrial and scientific pumps for pumping fluids, both liquids and gases, in very precise quantities or at very precise rates. More specifically it relates to valveless pumps where the "plug" volume remains constant and is repetitiously so at all speeds.
Prior art pumps have been designed, principally, according to one of two design criteria, reciprocating motion or rotary motion. Reciprocating pumps have incorporated a piston which operates within a cylinder. This piston has been driven off of a cam shaft or similar means to more reciprocatingly within the cylinder, the stroke displacement defining the volume of each "plug" of fluid moved through the pump.
While pumps may seem to operate continuously, when examined microscopically, they can be seen to cause discrete, contiguous volumes of "plugs" of fluid to move through the pump for each cycle of operation thereof. With critical applications a pump need to provide a precise discharge (output) pressure which is equivalent to saying it must pump repeatedly uniform plugs of the fluid and controlably variable speeds.
Reciprocating pumps utilize intake and exhaust valves. These valves present opportunities for leakage which may vary according to wear, pump size and speed of operation. This leakage is created when some of the fluid slips back or leaks and is not pumped along. In order to maintain more precise volume or rate pumping, a smaller reciprocating pump will be used which will have to be run at higher speeds for capacity. But higher speeds contribute to valve leakage as the valves are separate from the piston and cannot be precisely timed coordinately to piston operation at all speeds. While piston retreat causes the pump intake side to see an increasing chamber volume and to experience a vacuum during the intake operation; and piston advance causes the pump discharge side to see a decreasing chamber volume and experience a pressure during the exhaust operation, valve operation not absolutely precise. The piston stroke, therefore, does not precisely define "plug" size at all speeds, and in fact actual pumped plug size varies non-linearly with speed.
Rotary pumps have incorporated various devices to rotate within a housing creating a suction on one side (the intake) and a pressure on the other side (the discharge). Such devices include rotating eccentric pistons, rotating lobes, rotating vanes, rotating gears, rotating screws and rotating impellers. Rotary pumps essentially "scoop along" quantities of fluid causing a cavity which draws in more fluid to the intake location. Rotary pumps can be run at higher speeds than reciprocating pumps with less vibration but are subject to leakages, i.e., slippage.
Rotary pumps do not present a changing potential cylinder volume which causes a vacuum or void to draw in the fluid like a reciprocating pump. They present a fixed "scoop volume" which rotates around in and are causing a vacuum along the leading surface of the scoop and a pressure force along the trailing surface of the scoop. This pressure force tends to push fluid back out the intake causing slippage or leakage. While at the discharge side of a rotary pump the vacuum edge tends to drag fluid around again, away from the discharge. The performance characteristics (efficiency) including pumping rate of rotary pumps varies with speed.
Pinkerton, U.S. Pat. No. 3,257,953, has taught an alternative to reciprocating pumps and rotary pumps. The Pinkerton pump has a piston which oscillates back and forth through a defined angle while it also reciprocates. A complicated cam, lever and guide drive mechanism controls the operation of the Pinkerton piston. The Pinkerton pump can be characterized as a compound reciprocating pump whereby its piston reciprocates along the longitudinal axis of the cylinder while also reciprocating about an arc. Pinkerton has a second U.S. Pat. No. 3,168,872 patent.
What is desired, however, is a pump which provides the advantages of smooth high speed operation present with a rotary pump without the rotary pump disadvantage of fluid slip and which provides the advantages of positive displacement present in a reciprocating pump without the valve operation disadvantages.
An objective of this invention is to provide a pump which provides a positive displacement pumping operation without the use of valves.
A second objective of this invention is to have this valveless positive displacement pump operate with rotary motion.
A further objective of this invention is to provide this pump with a piston operating within a cylinder, this piston undergoing reciprocating motion as well as rotary motion.
An even further objective of this invention is to have this pump piston undergo a sinusoidal motion.